Slip ring assembly



May 1, 1951 Filed May 11, 1949 J. P. MADDEN SLIP RING ASSEMBLY 2 Sheets-Sheet 1 V INVENTOR. l5 ]6 .17

JOSEPH P MADDEN BY 1 M y 1951 J. P. MADDEN 2,551,030

SLIP RING ASSEMBLY Filed May 11, 1949 2 Sheets Sheet 2 f6 /5 JO [/9 (/6 13/ f7 INVENTOR. JOSEPH P MADDEN 4i "Mrm A 7' TOE'NEYS'.

Patented May 1, I951 UNITED STATES i PATiENT OFFICE- "SLIP RING ASSEMBLY Joseph P. Madden, Parma,-hio,:assignor to The I Cleveland Electric-Motorcompany, Cleveland,

Ohio, a corporation of Ohio Application May 11, 194-9, SerialN0. 92,649

.6 Claims. .1 This invention relates to a dynamoelectric machinehaving provision for efiectively trans- ;mitting air between the outboard end of the r0- ltoriand the interior of the machine along a path passingthrough theslip-ring assembly and, more particularly, to a :molded slip-ring assembly by .means of which this'may befaccornplished.

' Intthe pastgslip-ring assemblies have in some instances been .made of a molded material such xas a.syntheticresin; however such slip+ring assemblies have in1genera1 beentsubject to'thedefeet that the development in the assembly of high temperatures, :such, for'example, as temperaturesiin the neighborhood of 400 Fahren- 'heit,rtends to bring about :ibreak-down, r especially -under the influence 90f the electrical eonditions obtaining .inithe immediate 'vioinityof the sliprings and-ithe conductorsleading: from them. :Fc-r this reason, there shasibeen :a tendency to'avoid theluse .of .an integrally molded core, *notwith- ..'standingitsadvantages, in favorof acme made up .?of .several distinct parts, each separately imolcled, Tthe theory being that in .the event of Lbreak=downone or more of such separately moldedlpa'rts eantbeireplaced and the assemblyasa wholerreturned to operation. This, however, has given-riser to the possibility of separation between rthesseveral parts and-attendant misalignment of the islip-rings, .with .consequen jumping of thelbrushes; so that no wholly satisfactory solutionsihas heretofore been found to the problem of .making up v"a'unitary slip-ring assembly embodyingra molded core.

.Other defects have been found '.to reside in'or toifollow. from :the difiicultieszexperienced .by the :molderw in controlling as .accurately as required :the relative location of the slip-rings and 'the comparatively .narrow conductors leading :from them. Still another has :resided in .arcing or shQrt-circuiting arising out of :the accumulation .lb'etween the islip-rings of deposits of finelydivided metal Efrom ithe islip-ring's themselves and of :carbon ;dust "from zthe brushes :employed in c'onjunctionwith them. Still other defects have resulted :from relatively rotary .movement .between the slip-ring :assembly I as LEL'IWhOlB and the IOtOliShBQ-ffi on whichdt f is mounted, such move- .ment creating a 'conditionin' which the leads between the frotor'and :the conductors attached to ;.the." sliperings 'becomeisevered while the 'machine is in :operation, making .for:. more 2 serious trouble ".inathe .machineIitself.

iItdsian :object of the present invention :toob- \viate:thesezandiotherdefectssby'providing abacki ventilated sli'p'ringz'assembly io'f molded-'rconstrucother :design. 'It' is'ia further 'objeotro'f the. invention :to provide a .dynamo electric:machin-eschar- -aoterized by. a slip-ring assembly 'making provi- LSlOIlZfOl the effective transmittal 'oftair between the outboardendof the rotor'iand the. interior "of the vrnahine. I

Othernbiectszandiadvantages of the invention will be rapparentiffromithe descriptionzwhich follows and from the accompanying-drawings, "in 'which Figure .1 is "antend elevation :of the improved -slipering assembly of the present inventiona's seen fromfthe rotor; i.'.e.,the interionof the 'dynamo electric'machine. 'Figuref2 isca lon- "gitudinal section, with :parts in-1elevation, along .;line':22 oflFigurel, looking in ;the direction of the arrows. Figure 3 is.:a-'comp.osite longitudinal section, with parts in elevation, along-line 3-3 of FigureL'looking-in the directionof the .ar-

=rows. .Figure .4 isiaiside elevation of the improved slip-ringassembly of :the.-;present inven- 5 tion'asseen from liner-44of Figure 1.

As indicated inxFigure'l, :the improved .slipzring assembly of .thepresent invention consists, :among other things, :of an outer sleeve-like rannulusiinwhich are positioned the slip (collect- 40 ing)rings,'of whiehcthere'maybe ofirom two to "four orimore :but :usually :three; "an inner "sleeve-like annulus :spaced from the .outer: annulus by aplurality or 'arcuate passages extending longitudinally from one end .of the 'assemblyxto the other; andaplurality of relatively wide webs,

correspondingin number'tothe number of arouatepassages, 'which' are integral with and interconnect the inner and outer annuli. Embedded throughout practically their :entire lengths in '5o' the material'of Whiohthe core is moldedand located in the -Webs-1is a series of:.conductorsi'leading from "and corresponding in number to the number .of sliperingspeach .of such conductors 'Jtaking thelforml'of azgenerally :L-sha'ped stud "of massive proportions which is ithreaclejd itoward the outer end of its long shank and, at the outer end of its short shank, is bonded by a metallic bond to one of the slip-rings. The entire assembly is mounted by a key and key-way on the rotor shaft and, when so mounted, presents externally the appearance generally suggested by Figure 4.

Referring again to Figure 1,- major elements of the improved slip-ring assembly of the present invention thus include the outer sleeve-like annulus the inner sleeve-like annulus 2, a series of relatively wide webs 3, 4 and 5, and, separating the webs, a series of arcuate passages 65, 'i and 3. Like webs 3, 4 and 5, the latter are substantially (so-extensive as to length with inner and outer annuli and 2. Within inner annulus 2 is a longitudinally extending center opening 9 receiving the usual rotor shaft: such opening is provided with a lateral extension it of the nature of a key-way by which, in known fashion, the slip-ring assembly can be mounted on the rotor shaft. If, in a case in which the assembly is used for replacement, a small diameter shaft is encountered, a metal sleeve may be mounted on the shaft and the slip-ring assembly mounted on the sleeve.

Referring now to Figures 2, 3 and 4, other major elements include slip-rings l5, l6 and ll, which are positioned in spaced relation to each other in the periphery of outer annulus Such slip-rings'are in intimate contact with the material of which the core is molded and are held in place, among other things, by gripping action of such material on the knurled surfaces |8, I9 and 211 which characterize the inside of slip-rings |5, I6 and I1 respectively. To each of the three sliprings is attached a conductor, which, as pre- 'viously stated, takes the form of an L-shaped stud of massive proportions: such studsare necessarily of different lengths as a result of the fact that slip-rings l5, l6 and I! are located at different distances from the inboard end of the slip-ring assembly. Slip-ring I5, which is nearest the inboard end of the assembly, requires the shortest stud, such stud, shown in Figure 3, being designated 2|; slip-ring It requires a stud of intermediate length, designated 22, which stud appears in Figure 2; slip-ring ll, located farthest from the inboard end of the assembly, requires the longest stud, designated 23, which appears in Figure 3.

Except where the short shanks thereof extend toward and are bonded to the several slip-rings, studs 2 I, 22 and 23 extend in a direction generally parallel to the longitudinalaxis of the slip-ring assembly. Each stud is provided at the free or inboard end thereof with a threaded portion 2|a,

- 22a or- 23a, to which, as shown in Figure l, leads areconnected in the usual manner.

Studs 2|, 22 and 23 are located in webs 3, i and 5, being disposedapproximately mid-way between the inner surface of inner annulus 2 and the outer surface of outer annulus I.

Webs 3, Al and are somewhat longer, perhaps twice as long, in a circumferential direction than in the radial direction,

- this in order that studs 2|, 22 and 23 may, in so far aspossiblabe spaced by substantial distances from the surfaces of the slip-ring assembly.

As showntoward the top of Figure 2 and near the bottom of Figure 3, the nearest such surfaces are formed by the deep channels between adjacent slip-rings extending inward into the body of outer annulus to provide a place for the deposition-of debris; viz., metallic particles from the slip-rings and carbon dust from the brushes. Such channels, designated 33 and 3|, are located respectively between slip-rings I5 and I3 and between slip-rings l3 and ll: at the base thereof, a sufficient quantity of the material of which the core is formed overlies the stud or studs passing in proximity thereto to preclude the possibility of electrical discharges by way of channels 30 and 3|. Other surfaces are formed by the arcuate passages 3, 'l and 8 between adjacent webs; for example, between webs 3 and 4 is the generally arcuate passage 6 having rounded corners which give a blade-like aspect to the radially extending outer walls of Webs 3 and 4.

As indicated, outer annulus I, inner annulus 2 and webs 3, i and 5 are integral, being formed simultaneously by a molding operation accomplished by injecting a suitable molding compound into a mold in the manner hereinafter described. When the operation of molding the slip-ring as sembly has been completed, such molding compound is in intimate contact over the relatively large surface area thereof with each of studs 2|, 22 and 23 and, at the inboard ends of the studs, in contact also with the innermost threads of threaded portions 2 la, 22a and 23a. thereof. Over most of the inside surface of slip-rings l5, l6 and H; that is to say, knurled areas l8, l9 and 20, the molding compound of which the core is formed is in intimate contact with the slip-rings. In addition, the molding compound is preferably carried up around the outer edges of the two end rings, I5 and H to provide circumferentially extending shoulders 33 and 34 which help retain rings l5 and I! in place. Running radially through the core at some convenient point at the base of channel 3| is a threaded bore 35 through which a set screw (not shown) may be applied to the rotor shaft to preclude end-wise displacement of the slip-ring assembly.

In forming the core, it is convenient to use the base of the mold as a stud-carrying fixture, inserting in holes suitably located therein the threaded ends 2|a, 22a and 23a of studs 2|, 22 and 23. To the opposite ends of the studs will in the meanwhile have been attached slip-rings l5, it and ll, the latter being formed by cutting tubular stock into sections. Before cutting, the stock is knurled interiorly to provide knurled surfaces l8, l9 and 20. When the rings have been severed from the stock, studs 2|, 22 and 23 are bonded thereto with silver solder at a temperature of 1200 to 1400 degrees F., usually about 1300 degrees F. Thus when studs 2|, 22 and 23 are located as described with threaded portions 2|a, 22a and 23a thereof in suitable holes in the base of the mold, slip-rings l5, l6 and I1 will form a stack the elements of which lend themselves to easy alignment incident to assembly of the mold.

Mounted on or otherwise associated with the stud-carrying base of the mold will be three tapered inserts, arcuate in cross section, extending from the base of the mold to a point short of the medial plane of the completed assembly. Such inserts are for the purpose of forming arcuate cavities in the assembly, one such cavity, des ignated la, being indicated at the left in Figure 2. A series of like inserts is associated with the side or end walls of the mold, being adapted to leave cavities (such as that designated lb) in alignment with the cavities formed by the inserts on the mold base. In both instances, the inserts are tapered, the taper being such that the opening left by the insert is greater at the outer end of the assembly than near the medial plane. Between'the two sets of inserts will be a clearance offro'm to of an inch, provided to preclude interference between oppositely extending inserts. t

With studs 2 I, 2 2 and 23 mounted as described in the base of the mold and with slip-rings IS, IS and I! in substantial alignment, the side and end walls of the mold are next brought into apposition to the stack. The side walls of the mold will ordinarily be equipped with internally projecting ridges for forming channels 30 and 3t: being rounded in contour, such ridges slip easily into place between adjacent slip-rings and facilitate closing the walls of the mold around the stack by positioning the slip-rings in proper relation to each other. Preferably, but not necessarily, the mold includes two semi-circular side walls which are forced together and clamped in place to form the mold cavity. At the center of the mold will, of course, be a suitably shaped insert making provision for center opening 9 and key-way ID. The latter will preferably be tapered slightly, being larger at the outboard than at the inboard end of the assembly so as to facilitate removal of the insert from the assembly.

With'the studs and slip-rings located as described, with the various inserts in position, and with the side and end walls of the mold in place, a suitable molding compound may be injected into the mold and cured therein under heat and pressure. Preferably, but not necessarily, a fiberreinforced phenolic molding compound such as fiber-reinforced Bakelite is employed. The fibrous reinforcement may take the form of textile fibers of staple length, glass fibers, asbestos, macerated textile fabrics, etc., all of which may be introduced into the mold with the molding compound. If, as may be desired, sheets of textile fabric, woven glass fabric or like material are to be included as reinforcements in the core Curing takes place at conventional temperatures and pressures but requires a somewhat shorter period of time by virtue of the fact that presence of studs 2|, 22 and 23 and the several inserts reduces the maximum effective thickness of the core.

If desired, a metal sleeve (not shown) may be molded in place in the assembly immediately adjacent the inner surface of inner annulus 2.

When curing has been completed, the assembly may be removed from the mold and prepared for finishing. The preliminary operations include the removal of surface flash, punching out of the fiash 4D (indicated in dotted lines in Figure 2) formed between opposing arcuate inserts, and, if necessary, machining central opening 9. When these operations have been performed, establishing thereby an accurate center for the assembly, a skin cut is taken off rings [5, I6 and l! to-correct for possible misalignment. By machining rings l5, l6 and I! together, their exter-nal surfaces will be in alignment, thereby minimizing the likelihood of jumping of the brushes when the assembly is employed in a dynamoelectric machine. Such other finishing operations as may be desirable are performed at this stage.

When it is desired to install the assembly on the rotor shaft of a dynamoelectric machine, the key 4| (indicated in dotted lines in Figure 2) is located in place in the key-way of therotor-eshaft and the rotor assembly eased into position with key-way [0 in alignment with key M. Since the central opening 6 will be slightly larger atthe outboard end of the assembly than at the inboard end, the key will seat itself somewhat to the left of center as suggested in Figure 2. This having been done, a set screw is introduced through bore 35, after which the open-end ofbor'e 3'r5overs lying the end of the set screw is sealedwithzsome suitable sealing compound 42. The leads 43, M and 45 to the rotor are then made fast to thread:- ed portions 21a, 22a and 23a, after the slip-ring assembly is'ready for operation.

In use, arcuate passages 6, l and 8 serveto promote movement of air between the interior of the machine and the outboard end of the slipring assembly, thereby increasing the capacity of the rings. The normal direction of movement will be from the outboard end of the assembly toward the interior of the machine, although in special circumstances, depending in part on the construction of the housing, the direction of air movement may be reversed so that air is trans.- mitted from the interior of the machine toward the outboard end of the assembly. In either case, the effect is to reduce very substantially the operating temperature at which the assembly runs. Lacking passages of the nature of arcuate passages G, T and 8, a temperature of about 40f) F. is likely to be developed at 3600 R. P.'M.; with such passages provided, the assembly can be expected to operate at a temperature below about 300 F. One important result is to delay or preclude breakdown; another, to preclude the likelihood, present in certain of the prior art devices, of separation of parts making up the complete assembly.

It is apparent that numerous modifioationsmay be made without departing from the spirit of and IT, as well as the studs connected to them,.

will be of red brass, although various other metals, such as bronze, may be employed instead. The shape of passages e, l and 8 need not necessarily be arcuate nor need the corners be rounded, although, as indicated, rounded corners contribute to the blade-like aspect of the radially extending outer walls of webs 3, 4 and 5. The number of slip-rings may vary from two to four or more, although three slip-rings are usually present in the ordinary poly-phase dynamoelectric machine.

- the outboard end of the rotor and the interior of the machine comprising a sleeve-like outer annulus having on its exterior surface a plurality of collector rings separated by channels extending deep into the body of the outer annulus, the inner faces of said rings having their surfaces roughened to enhance the grip between the rings and the outer annulus; a sleeve-like inner annulus spaced from the outer annulus by a plurality of arcuate passages extending from one end of the assembly to the other; a plurality of rela- 7 tively-wide webs, not less -in number than the number of arcuate passages, integral with and interconnecting the outer annulus and the inner annulus, said webs and said annuli being substantially foo-extensive in length; and, embedded throughout practically all of the lengths thereof in thefmaterial of which the. assembly is molded and spaced by virtue of the width of the webs by substantial distances from the surfaces of the slip-ring assembly, a plurality of massively formed studs located in said webs, said studs being L 'shaped and having the end faces of the short legs thereof held by metallic bonds to the roughened faces of the collector rings.

2. A molded slip-ring assembly for a dynamoelectric machine comprising an outer annulus having'on its exterior surface a plurality of collector 1 rings separated by channels extending deep into the body of the outer annulus, the inner faces of said rings having their surfaces roughened to enhance the grip between the rings and the outer annulus; anlinner annulus spaced from the outer annulus by a plurality of passages extending from one end of the assembly to the other; a plurality of relatively wide webs, not less in number than the number of passages, integral with and interconnecting the outer antwins and the inner annulus; and, located in said webs, a plurality of massively formed studs embedded throughout practically all of the lengths l thereof I in the material of which the assembly is molded and spaced by virtue of the width of the webs by substantial distances from the surfaces of the slip-ring assembly, said studs being legs thereof held by metallic bonds to the roughe'ned faces of the collector rings.

3. A molded slip-ring assembly for a dynamoelectric machine comprising an outer annulus having on its exterior surface a plurality of collector rings separated by channels, the inner faces of said rings having their surfaces roughened to enhance the grip between the rings and the outer annulus; an inner annulus spaced from the outer annulus by a plurality of passages extendingfrom one end of the assembly to the other; a plurality of relatively wide webs, not less in number than the number of passages, integralw'ith and interconnecting the outer annulus and the inner annulus; and, located in said webs, a plurality of massively formed studs embedded throughout practically all of the lengths thereof in the material of which the assembly is molded and spaced by virtue of the width of the webs by substantial distances from the surfaces of the slip-ring assembly, said studs being L-shaped and having the end faces of the short legs thereof held by metallic bonds to the roughened faces of the collector rings.

4. A molded slip-ring assembly for a dynamoelectric machine comprising an outer annulus having on its exterior surface a plurality of collec'tdr'rings, the inner faces of said rings having their surfaces roughened to enhance the grip between the rings and the outer annulus; an inner annulus spaced from the outer annulus by a plurality of passages extending from one end L-shaped and having the end fac'es'cf the short of the assembly to the other; a plurality of-relatively wide webs integral with and interconnecting the outer annulus and the inner annulus; and, located in said webs, a plurality of massively formed studs embedded in the material of which the assembly is molded and spaced by virtue of the width of the webs by substantial distances from the surfaces of the slip-ring assembly, said studs being L-shaped and having the end faces of the short legs thereof held by metallic bonds to the roughened faces of the collector rings.

5. A molded slip-ring assembly for a dynamoelectric machine comprising an outer annulus having on its exterior surface a plurality of collector rings, the inner faces of said rings having their surfaces roughened to enhance the grip between the rings and the out-er annulus; an inner annulus spaced from the outer annulus by a plurality of passages extending from one end of the assembly to the other; a plurality of relatively wide webs integral with and interconnecting. the outer annulus and the inner'annulus; and, located in said webs, a plurality of massively formed studs spaced by virtue of the width of the webs by substantial distances from the surfaces of the slip-ring assembly, said studs being L-shaped and having the end faces of the short legs thereof held by metallic bonds to the roughened faces of the collector rings.

6. A molded slip-ring assembly for a dynamoelectric machine comprising an outer annulus having on its exterior surface plurality of collector rings, the inner faces of said rings having their surfaces roughened to enhance the grip between the rings and the outer annulus; an inner annulus spaced from the outer annulus by a plurality of passages extending from one end of the assembly to the other; a plurality of relatively wide webs integral with and inter,- connecting the outer annulus and the inner annulus; and, located in said webs, a pluralityof studs spaced by virtue of the width of the webs by substantial distances from the surfaces of the slip-ring assembly, said studs being L-shaped and having the end faces of the short legs there of held by metallic bonds to the roughened faces of, the collector rings.

JOSEPH MADDEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Netherlands Nov. 15, 1938 

